1. Field of the Invention
The present invention relates generally to spin valve sensors for magnetic heads, and more particularly to an improved NiFeCr seed layer for a PtMn spin valve sensor structure.
2. Description of the Prior Art
Magnetic heads for hard disk drives typically include a magnetoresistive read head element for reading data from the disk of the hard disk drive. The present invention specifically relates to the use of a spin valve sensor structure as the magnetoresistive element. As is well known to those skilled in the art, such spin valve sensor structures include a plurality of thin film layers having particular magnetic properties, and which are sensitive to the magnetic field of the data bits of a hard disk. A typical spin valve sensor will include at least one antiferromagnetic layer, at least one pinned magnetic field layer, and at least one free magnetic field layer. When the magnetic field direction of the free magnetic field layer is parallel to the magnetic field direction of the pinned magnetic field layer, the electrical resistance R of the spin valve sensor is lowest. When reading data, a magnetic data bit of a hard disk will cause the magnetic field direction of the free magnetic field layer to change, whereupon the electrical resistance of the spin valve sensor increases. This change in resistance (ΔR) affects the electrical current passing through the spin valve sensor, and is thus detected as a data signal. It is desirable to develop spin valve sensors having an increased ΔR/R value, as such spin valve sensors are generally more sensitive. Another parameter that is significant in spin valve sensor performance is the free layer coercivity of the spin valve sensor, and generally, the lower the coercivity, the more stable the spin valve sensor will be.
Many different materials have been utilized in the prior art in attempts to increase ΔR/R and reduce the coercivity of the spin valve sensor. The present invention relates to a spin valve sensor that is fabricated utilizing a particular seed layer composed of NiFeCr, together with a seed layer etching process step which affects the crystalline surface structure of the seed layer. An improved crystalline structure within the spin valve sensor layers deposited upon the seed layer is thereby created which results in a more desirable spin valve sensor having an increased ΔR/R together with a reduced coercivity.